We thank the laboratorians, epidemiologists, and affiliates with public health departments for sample submissions to the Centers for Disease Control and Prevention. The findings and conclusions in this report are those of the authors and do not necessarily represent the official position of the Centers for Disease Control and Prevention. Use of trade names and commercial sources are for identification only and do not imply endorsement by the Centers for Disease Control and Prevention.

While the IHC protocol was performed on formalin-fixed tissues, which inactivates RABV if present, appropriate biosafety protocols should be properly followed. All biosafety procedures are described in the Biosafety in Microbiological and Biomedical Laboratories (BMBL) 5th Edition (https://www.cdc.gov/biosafety/publications/bmbl5/index.htm), including wearing proper personal protective equipment (PPE), and vaccination requirement as described12. In addition, proper containment and handling of hazardous chemicals (like formalin, AEC and xylene), should be followed (e.g., fume hoods).
1. Formalin fixation of tissues
<ol>
	<li>Place 3-5 mm brain tissues collected after necropsy13 into 10% phosphate buffered formalin solution (1:20 to 1:50 tissue/formalin ratio) for 24-72 h. 
	CAUTION: Formalin is a toxic fixative.</li>
	<li>Record the approximate tissue weight (size), tissue type (brain areas) and volume of formalin. It is important for laboratories to document and maintain records on fixation times.</li>
	<li>For longer tissue storage after formalin fixation and prior to processing, place the tissue in 70% ethanol.</li>
</ol>
2. Tissue processing
<ol>
	<li>Following the specimen fixation, dissect the tissue to include the important brain areas e.g., cross sections of the brainstem, cerebellum (3 lobes), or the hippocampus (both hippocampi) each cut 3 to 5 mm thick and placed into processing cassettes.</li>
	<li>Process the tissue cassettes for paraffin wax infiltration, embedded into paraffin blocks and sectioned (3 to 6 &#181;m) on a microtome.</li>
</ol>
3. Preparation of Materials / Staining dishes
<ol>
	<li>Set up the staining dish14 (Table of Materials) as shown in Figure 1. Fill each dish with 250 mL of the solution.</li>
	<li>Preparation of the 3-Amino-9-ethylcarbizole (AEC) substrate stock solution
	<ol>
		<li>Dissolve one 20 mg tablet of 3-amino 9-ethylcarbazole (AEC) into 5 mL of N,N, dimethylformamide using a glass pipette. 
		CAUTION: AEC is a carcinogen.</li>
	</ol>
	</li>
	<li>Preparation of the protease (e.g., Pronase) stock solution for the antigen retrieval
	<ol>
		<li>Dissolve 7 mg of the protease in 200 mL of PBS.</li>
	</ol>
	</li>
	<li>Preparation of the rinse buffer PBS-T
	<ol>
		<li>Add 10 mL of Tween 80 to 990 mL of PBS. Mix it well to form a homogenous solution.</li>
	</ol>
	</li>
</ol>
4. Deparaffinization and tissue rehydration
<ol>
	<li>Make 5 &#181;m paraffin section using a microtome, float it on a water bath at 38 &#730;C and collect on to glass slides. Label the slides with a reagent resistant pen/marker.</li>
	<li>Place the slides onto a tray and melt in a 55-60 &#730;C oven for 1 h. Do not raise the temperature above 60 &#730;C as it can destroy the viral antigen.</li>
	<li>Remove slides from the oven and immediately deparaffinize in 3 consecutive xylene rinses of 5 min each in the dishes 1, 2 and 3.</li>
	<li>Rehydrate the sections on the slide by sequential immersions in decreasing dilution of ethanol to deionized water: (4 through 11 is a dip rinse) dish 4: xylene/100% ethanol (1:1); dish 5: 100% ethanol; dish 6: 100% ethanol; dish 7: 95% ethanol; dish 8: 95% ethanol; dish 9: 80% ethanol; dish 10: 70% ethanol; dish 11: deionized water (Figure 1. Dish set-up). 
	CAUTION: Xylene is a hazardous chemical and work should be conducted in a fume hood.</li>
</ol>
5. Proteolytic antigen retrieval
<ol>
	<li>Treat slides with the protease (2.5 &#181;g/mL of PBS) for 30 min for proteolytic antigen retrieval in dish 12.</li>
	<li>Then rinse in PBS-T for 10 min (dish 13).</li>
	<li>Treat with 3% hydrogen peroxide for 10 min (dish 14).</li>
	<li>Again, wash with PBS-T for 10 min (dish 15).</li>
</ol>
6. Staining procedure
<ol>
	<li>Handle slides one at a time keeping the remaining slides submerged in the buffer (do not remove the whole slide holder - keep slides wet). Remove one slide and blot off excess buffer (using a paper towel) from around the tissue section being careful not to disturb the tissue section. Incubate slides in a humidity chamber, made by placing moistened paper towels, on the lab bench top14 at room temperature with normal goat serum (blocking) for 15 min.</li>
	<li>Incubate with the optimal pre-determined dilution primary anti-rabies antibody (1:250 dilution of mouse anti-rabies serum, unpublished) (positive control) and negative control antibodies at room temperature same as above (step 6.1.) for 60 min with no washes in between.</li>
	<li>After 60 min, wash with PBS-T for 10 min (dish 16).</li>
	<li>Incubate with the biotinylated antibody (species specific) in a humidity chamber at room temperature for 15 min (handling same as step 6.1.).</li>
	<li>Wash with PBS-T for 10 min (dish 16).</li>
	<li>Incubate with Streptavidin-HRP complex in a humidity chamber at room temperature for 15 min (handling same as 6.1.).</li>
	<li>Wash with PBS-T for 10 min (dish 16).</li>
	<li>Incubate with peroxidase substrate, amino-ethylcarbazole (AEC), in a humidity chamber at room temperature for 10 min. Make AEC just prior to use. To do so, add 1 mL of AEC stock solution to 14 mL of 0.1M acetate buffer, pH 5.2. Add 0.15 mL of 3% H2O2. Filter the mixture just before use (0.45 &#181;m filter). 
	NOTE: The working solution of AEC is only stable for 2-3 h. The AEC stock solution can be stored in the refrigerator for longer periods.</li>
	<li>Wash in deionized water 10 min (dish 17)</li>
	<li>Counterstained with Gill&#39;s Hematoxylin diluted 1:2 with deionized water for 2 min (dish 18).</li>
	<li>Rinse off excess Hematoxylin with deionized water dip rinse (dish 19 and 20).</li>
	<li>Rinse in Scott&#39;s Tap water 30 s (bluing solution) dish 21.</li>
	<li>Wash in deionized water 10 min (dish 22)</li>
	<li>Remove slides one at a time - mount with water-soluble mounting medium.</li>
	<li>Read slides on a light microscope.</li>
</ol>

<ol>
	<li>Rupprecht, C., Kuzmin, I., Meslin, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Lyssaviruses+and+rabies:+current+conundrums,+concerns,+contradictions+and+controversies.">Lyssaviruses and rabies: current conundrums, concerns, contradictions and controversies.</a> F1000Research. 6, 184 (2017).</li><li>Fooks, A. R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Current+status+of+rabies+and+prospects+for+elimination.">Current status of rabies and prospects for elimination.</a> Lancet. 384 (9951), 1389-1399 (2014).</li><li>Finke, S., Brzozka, K., Conzelmann, K. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tracking+fluorescence-labeled+rabies+virus:+enhanced+green+fluorescent+protein-tagged+phosphoprotein+P+supports+virus+gene+expression+and+formation+of+infectious+particles.">Tracking fluorescence-labeled rabies virus: enhanced green fluorescent protein-tagged phosphoprotein P supports virus gene expression and formation of infectious particles.</a> Journal of Virology. 78 (22), 12333-12343 (2004).</li><li>WHO. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=WHO+Expert+Consulation+on+Rabies,+Third+Report.">WHO Expert Consulation on Rabies, Third Report.</a> WHO Technical Report Series. 1012, 1 (2018).</li><li>Goldwasser, R. A., Kissling, R. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fluorescent+antibody+staining+of+street+and+fixed+rabies+virus+antigens.">Fluorescent antibody staining of street and fixed rabies virus antigens.</a> Proceedings of the Society for Experimental Biology and Medicine. 98 (2), 219-223 (1958).</li><li>Lembo, T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evaluation+of+a+direct,+rapid+immunohistochemical+test+for+rabies+diagnosis.">Evaluation of a direct, rapid immunohistochemical test for rabies diagnosis.</a> Emerging Infectious Diseases. 12 (2), 310-313 (2006).</li><li>Fekadu, M., Greer, P. W., Chandler, F. W., Sanderlin, D. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Use+of+the+avidin-biotin+peroxidase+system+to+detect+rabies+antigen+in+formalin-fixed+paraffin-embedded+tissues.">Use of the avidin-biotin peroxidase system to detect rabies antigen in formalin-fixed paraffin-embedded tissues.</a> Journal of Virological Methods. 19 (2), 91-96 (1988).</li><li>Hamir, A. N., Moser, G., Rupprecht, C. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+five+year+(1985-1989)+retrospective+study+of+equine+neurological+diseases+with+special+reference+to+rabies.">A five year (1985-1989) retrospective study of equine neurological diseases with special reference to rabies.</a> Journal of Comparative Pathology. 106 (4), 411-421 (1992).</li><li>Inoue, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cross-reactive+antigenicity+of+nucleoproteins+of+lyssaviruses+recognized+by+a+monospecific+antirabies+virus+nucleoprotein+antiserum+on+paraffin+sections+of+formalin-fixed+tissues.">Cross-reactive antigenicity of nucleoproteins of lyssaviruses recognized by a monospecific antirabies virus nucleoprotein antiserum on paraffin sections of formalin-fixed tissues.</a> Pathology International. 53 (8), 525-533 (2003).</li><li>Webster, J. D., Miller, M. A., Dusold, D., Ramos-Vara, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effects+of+prolonged+formalin+fixation+on+diagnostic+immunohistochemistry+in+domestic+animals.">Effects of prolonged formalin fixation on diagnostic immunohistochemistry in domestic animals.</a> Journal of Histochemistry and Cytochemistry. 57 (8), 753-761 (2009).</li><li>Feiden, W., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Immunohistochemical+staining+of+rabies+virus+antigen+with+monoclonal+and+polyclonal+antibodies+in+paraffin+tissue+sections.">Immunohistochemical staining of rabies virus antigen with monoclonal and polyclonal antibodies in paraffin tissue sections.</a> Zentralblatt fur Veterinarmedizin Reihe B. 35 (4), 247-255 (1988).</li><li>Manning, S. E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Human+rabies+prevention--United+States,+2008:+recommendations+of+the+Advisory+Committee+on+Immunization+Practices.">Human rabies prevention--United States, 2008: recommendations of the Advisory Committee on Immunization Practices.</a> Morbidity and Mortality Weekly Reports Recommendations and Reports. 57, 1-28 (2008).</li><li>WHO. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Laboratory techniques in rabies. 1, 67-72 (2018).</li><li>Patrick, E. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Enhanced+Rabies+Surveillance+Using+a+Direct+Rapid+Immunohistochemical+Test.">Enhanced Rabies Surveillance Using a Direct Rapid Immunohistochemical Test.</a> Journal of Visualized Experiments. (146), (2019).</li><li>Whitfield, S. G., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+comparative+study+of+the+fluorescent+antibody+test+for+rabies+diagnosis+in+fresh+and+formalin-fixed+brain+tissue+specimens.">A comparative study of the fluorescent antibody test for rabies diagnosis in fresh and formalin-fixed brain tissue specimens.</a> Journal of Virology Methods. 95 (1-2), 145-151 (2001).</li><li>WHO. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Diagnostic procedures for antigen detection. , (2016).</li><li>Jarvis, J. A., Franke, M. A., Davis, A. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rabies+direct+fluorescent+antibody+test+does+not+inactivate+rabies+or+eastern+equine+encephalitis+viruses.">Rabies direct fluorescent antibody test does not inactivate rabies or eastern equine encephalitis viruses.</a> Journal of Virology Methods. 234, 52-53 (2016).</li></ol>

The authors have nothing to disclose.

Due to the high fatality rate of rabies after the symptom onset, the diagnosis of suspect animals for RABV infection is extremely critical for an appropriate post-exposure prophylactic treatment. Rabies diagnosis primarily depends on DFA, DRIT, and PCR-based techniques using fresh or frozen tissues. For testing of formalin-fixed tissues, the IHC test provides an alternative method for the sensitive and specific detection of RABV antigen. While the tissues fixed in formalin have proteins stabilized due to the modification...

Rabies is an acute progressive encephalitis caused by the negative sense RNA viruses belonging to the genus lyssavirus1. Nearly 99% of all human deaths caused by the infection with rabies virus (RABV), the type member of the genus, is transmitted by dogs2. Rabies diagnosis of suspect animals relies on the detection of antigen (primarily viral encoded nucleoprotein, N protein) in complex with genomic RNA (ribonucleoprotein complex, RNP) in the brain tissue3. The antigen detection by the direct fluorescent antibody (DFA) test is considered the gold standard for rabies diagnosis4. The method utilizes fresh or fresh frozen brain material, a touch impression on a slide, fixation in acetone, staining using commercially available fluorescent isothiocyanate (FITC) labeled monoclonal or polyclonal antibodies (mAbs/pAbs) and read by the fluorescence microscopy5. The DFA test is rapid, sensitive, and specific for rabies antigen detection in fresh brain tissue. Recently, a direct rapid immunohistochemical test (DRIT), modified immunohistochemistry (IHC) technique, was demonstrated to exhibit similar sensitivity to DFA but offers the advantage of light microscopy for visualization6. While the detection method used in DRIT, is similar to IHC, the initial step utilizes fresh or frozen tissues to generate touch impressions of the sample followed by fixation in formalin.
IHC is a widely used technique to determine histological changes and detection of proteins using specific antibodies in formalin-fixed tissues embedded in paraffin blocks. IHC is an established alternative test for the rabies antigen detection in the tissue sections7. IHC has been particularly utilized for the diagnosis of retrospective cases that exhibited neurological diseases to determine the burden of rabies8. Paraffin-embedded formalin-fixed tissues preserve the proteins for the detection even after several years when stored at ambient temperature9. Formalin treatment modifies proteins by cross-linking and altering the amino acid side chains, which might make the epitopes no longer reactive against antibodies10. While the IHC test for rabies antigen detection involves either mAbs or pAbs, the latter is advantageous as multiple epitopes and divergent lyssaviruses can be detected11.
The standard steps involved in IHC are formalin fixation of tissues, embedding in paraffin blocks, sectioning of tissues, deparaffinization and hydration, epitope recovery, reactivity against primary and secondary antibodies, and the development using chromogenic substrates. This manuscript describes a detailed account of the protocol for rabies diagnosis. For rabies antigen detection, mouse serum immunized with RABV (pAbs) generated at the U.S. Centers for Disease Control and Prevention (CDC) Atlanta, Georgia, in combination with biotinylated anti-mouse secondary antibodies are utilized. Biotinylated Abs are detected by the addition of streptavidin-horseradish peroxidase (HRP) complex followed by the color development with amino-ethylcarbazole substrate.

<table><tbody><tr><td>3% hydrogen peroxide</td><td>Pharamacy brands</td><td></td><td>Off the shelf 3% H2O2</td></tr><tr><td>3-Amino-9-ethylcarbazole (AEC)</td><td>Millipore Sigma</td><td>A6926</td><td></td></tr><tr><td>Acetate Buffer pH 5.2</td><td>Poly Scientific R&amp;amp;D Corp.</td><td>s140</td><td></td></tr><tr><td>Buffered Formalin 10% Phosphate Buffered</td><td>Fisher Scientific</td><td>SF100-4</td><td>Certified</td></tr><tr><td>Cover slips Corning</td><td>Fisher Scientific</td><td>12-553-471</td><td>24 X 50 mm</td></tr><tr><td>Ethanol 190 Proof</td><td>Pharmco-AAPER</td><td>111000190</td><td></td></tr><tr><td>Ethanol 200 Proof</td><td>Pharmco-AAPER</td><td>111000200</td><td></td></tr><tr><td>Gill&#039;s hematoxylin formulation #2</td><td>Fisher Scientific</td><td>CS401-1D</td><td></td></tr><tr><td>HistoMark Biotin-Streptavidin Peroxidase Kit</td><td>seracare</td><td>71-00-18</td><td>Mouse Primary Antibody&amp;nbsp;</td></tr><tr><td>ImmunoHistoMount</td><td>Millipore Sigma</td><td>i1161</td><td>Mounting media</td></tr><tr><td>N,N, Dimethyl formamide GR</td><td>Fisher Scientific</td><td>D119</td><td></td></tr><tr><td>Phosphate Buffered Saline&amp;nbsp;</td><td>HyClone</td><td>RR14440.01</td><td>01M, pH 7.2 (pH 7.2-7.6)</td></tr><tr><td>Plan-APOCHROMAT 40X/0.95 Objective</td><td>Multiple vendors</td><td></td><td></td></tr><tr><td>Plan-APOCHROMATIC 20X/0.75 Objective</td><td>Multiple vendors</td><td></td><td></td></tr><tr><td>Pronase</td><td>Millipore Sigma</td><td>53702</td><td>Protease, &lt;em&gt;Streptomyces griseus&lt;/em&gt;</td></tr><tr><td>Scott&#039;s Tap Water&amp;nbsp;</td><td>Poly Scientific R&amp;amp;D Corp.</td><td>s1887</td><td></td></tr><tr><td>Tissue-Tek Slide stain set</td><td>Fisher Scientific</td><td>50-294-72</td><td></td></tr><tr><td>TWEEN-80&amp;nbsp;</td><td>Millipore Sigma</td><td>P1754</td><td></td></tr><tr><td>Xylene</td><td>Fisher Scientific</td><td>X3S-4</td><td>Histological Grade</td></tr><tr><td>Zeiss Axioplan 2 imaging - microscope</td><td>Multiple vendors</td><td></td><td></td></tr></tbody></table>

immunohistochemistry test for the lyssavirus antigen detection from formalin-fixed tissues

One of the primary diagnostic modalities for rabies is the detection of viral ribonucleoprotein (RNP) complex (antigen) in the infected tissue samples. While the direct fluorescent antibody (DFA) test or the direct rapid immunohistochemical test (DRIT) are most commonly utilized for the antigen detection, both tests require fresh and/or frozen tissues for impressions on slides prior to the antigen detection using antibodies. If samples are collected and fixed in formalin, neither test is optimal for the antigen detection, however, testing can be performed by conventional immunohistochemistry (IHC) after embedding in paraffin blocks and sectioning. With this IHC method, tissues are stained with anti-rabies antibodies, sections are deparaffinized, antigen retrieved by partial proteolysis or other methods, and incubated with primary and secondary antibodies. Antigens are stained using horseradish peroxidase / amino ethyl carbazole and counterstained with hematoxylin for the visualization using a light microscope. In addition to the specific antigen detection, formalin fixation offers other advantages like the determination of histological changes, relaxed conditions for specimen storage and transport (under ambient temperatures), ability to test retrospective cases and improved biological safety through the inactivation of infectious agents.

Figure 2 demonstrates representative IHC staining results of positive and negative control samples in different brain tissues tested. Figure 2A,D,G represent positive samples at 200x, while Figure 2B,E,H correspond to 400x magnification, respectively. Figure 2A-C correspond to the brainstem; Figure 2...

Watch this Scientific Journal Video about Immunohistochemistry Test for the Lyssavirus Antigen Detection from Formalin-Fixed Tissues at JoVE.com

Immunohistochemistry Test for the Lyssavirus Antigen Detection from Formalin-Fixed Tissues

Here, we present an immunohistochemistry test protocol for the detection of rabies virus antigen as an alternative diagnostic test for formalin-fixed tissues.

One of the primary diagnostic modalities for rabies is the detection of viral ribonucleoprotein (RNP) complex (antigen) in the infected tissue samples. ...

immunohistochemistry-test-for-lyssavirus-antigen-detection-from

Research

JoVE Journal

Immunology and Infection

4.2K Views.  Centers for Disease Control and Prevention. Here, we present an immunohistochemistry test protocol for the detection of rabies virus antigen as an alternative diagnostic test for formalin-fixed tissues.

Video: Immunohistochemistry Test for the Lyssavirus Antigen Detection from Formalin-Fixed Tissues

Evaluation of a Universal Nested Reverse Transcription Polymerase Chain Reaction for the Detection of Lyssaviruses

To detect rabies virus and other member species of the genus Lyssavirus within the family Rhabdoviridae, the pan-lyssavirus nested reverse transcription polymerase chain reaction (nested RT-PCR) was developed to detect the conserved region of the nucleoprotein (N) gene of lyssaviruses. The method applies reverse transcription (RT) using viral RNA as template and oligo (dT)15 and random hexamers as primers to synthesize the viral complementary DNA (cDNA). Then, the viral cDNA is used as a template to amplify an 845 bp N gene fragment in first-round PCR using outer primers, followed by second-round nested PCR to amplify the final 371 bp fragment using inner primers. This method can detect different genetic clades of rabies viruses (RABV). The validation, using 9,624 brain specimens from eight domestic animal species in 10 years of clinical rabies diagnoses and surveillance in China, showed that the method has 100% sensitivity and 99.97% specificity in comparison with the direct fluorescent antibody test (FAT), the gold standard method recommended by the World Health Organization (WHO) and the World Organization for Animal Health (OIE). In addition, the method could also specifically amplify the targeted N gene fragment of 15 other approved and two novel lyssavirus species in the 10th Report of the International Committee on Taxonomy of Viruses (ICTV) as evaluated by a mimic detection of synthesized N gene plasmids of all lyssaviruses. The method provides a convenient alternative to FAT for rabies diagnosis and has been approved as a National Standard (GB/T36789-2018) of China.

A pan-lyssavirus nested reverse transcription polymerase chain reaction has been developed to detect specifically all known lyssaviruses. Validation using rabies brain samples of different animal species showed that this method has a sensitivity and specificity equivalent to the gold standard fluorescent antibody test and could be used for routine rabies diagnosis.

To detect rabies virus and other member species of the genus Lyssavirus within the family Rhabdoviridae, the pan-lyssavirus nested reverse transcription ...

Genetics

Standard Operating Procedure for Lyssavirus Surveillance of the Bat Population in Taiwan

Viruses within the genus Lyssavirus are zoonotic pathogens, and at least seven lyssavirus species are associated with human cases. Because bats are natural reservoirs of most lyssaviruses, a lyssavirus surveillance program of bats has been conducted in Taiwan since 2008 to understand the ecology of these viruses in bats. In this program, non-governmental bat conservation organizations and local animal disease control centers cooperated to collect dead bats or bats dying of weakness or illness. Brain tissues of bats were obtained through necropsy and subjected to direct fluorescent antibody test (FAT) and reverse transcription polymerase chain reaction (RT-PCR) for detection of lyssavirus antigens and nucleic acids. For the FAT, at least two different rabies diagnosis conjugates are recommended. For the RT-PCR, two sets of primers (JW12/N165-146, N113F/N304R) are used to amplify a partial sequence of the lyssavirus nucleoprotein gene. This surveillance program monitors lyssaviruses and other zoonotic agents in bats. Taiwan bat lyssavirus is found in two cases of the Japanese pipistrelle (Pipistrellus abramus) in 2016&#8211;2017. These findings should inform the public, health professionals, and scientists of the potential risks of contacting bats and other wildlife.

This protocol introduces a standard laboratory operating procedure for diagnostic testing of lyssavirus antigens in bats in Taiwan.

Viruses within the genus Lyssavirus are zoonotic pathogens, and at least seven lyssavirus species are associated with human cases. Because bats are ...

Environment

Immunohistochemical Analysis in the Rat Central Nervous System and Peripheral Lymph Node Tissue Sections

Immunohistochemistry (IHC) provides highly specific, reliable and attractive protein visualization. Correct performance and interpretation of an IHC-based multicolor labeling is challenging, especially when utilized for assessing interrelations between target proteins in the tissue with a high fat content such as the central nervous system (CNS).
Our protocol represents a refinement of the standard immunolabeling technique particularly adjusted for detection of both structural and soluble proteins in the rat CNS and peripheral lymph nodes (LN) affected by neuroinflammation. Nonetheless, with or without further modifications, our protocol could likely be used for detection of other related protein targets, even in other organs and species than here presented.

We here present an optimized, detailed protocol for double immunostaining in formalin-fixed, paraffin-embedded rat central nervous system (CNS) and peripheral lymph node (LN) tissue sections.

Immunohistochemistry (IHC) provides highly specific, reliable and attractive protein visualization. Correct performance and interpretation of an IHC-based ...

Neuroscience

A Technique to Simultaneously Visualize Virus-Specific CD8+ T Cells and Virus-Infected Cells In situ

The numbers and locations of virus-specific CD8+ T cells relative to the numbers and locations of their infected cell targets is thought to be critical in determining outcomes that range from clearance to chronic persistent infections. We describe here a method for assessing the spatial and quantitative relationships between immune effector (E) virus-specific CD8+ T cells and infected targets (T) that combines in situ tetramer (IST) staining to detect virus-specific CD8+ T cells and in situ hybridization (ISH) to detect viral-RNA+ cells in the tissues where the battle between immune defenses and infection takes place. The combination of IST staining and ISH, abbreviated ISTH, enables visualization and mapping of the locations of immune effector cells and targets, and facile determination of E:T ratios.  These parameters in turn can then be used to determine the relationships between spatial proximity, and the timing and magnitude of the immune response that predict outcomes in early infection.

A Technique to Simultaneously Visualize Virus-Specific CD8+ T Cells and Virus-Infected Cells In situ

A technique combining in situ tetramer staining and in situ hybridization (ISTH) enables visualization, mapping and analysis of the spatial proximity of virus-specific CD8+ T cells to their virus-infected targets, and determination of the quantitative relationships between these immune effectors and targets to infection outcomes.

The numbers and locations of virus-specific CD8+ T cells relative to the numbers and locations of their infected cell targets is thought to be critical in ...

Biology

Detection of the Genome and Transcripts of a Persistent DNA Virus in Neuronal Tissues by Fluorescent In situ Hybridization Combined with Immunostaining

Single cell codetection of a gene, its RNA product and cellular regulatory proteins is critical to study gene expression regulation. This is a challenge in the field of virology; in particular for nuclear-replicating persistent DNA viruses that involve animal models for their study. Herpes simplex virus type 1 (HSV-1) establishes a life-long latent infection in peripheral neurons. Latent virus serves as reservoir, from which it reactivates and induces a new herpetic episode. The cell biology of HSV-1 latency remains poorly understood, in part due to the lack of methods to detect HSV-1 genomes in situ in animal models. We describe a DNA-fluorescent in situ hybridization (FISH) approach efficiently detecting low-copy viral genomes within sections of neuronal tissues from infected animal models. The method relies on heat-based antigen unmasking, and directly labeled home-made DNA probes, or commercially available probes. We developed a triple staining approach, combining DNA-FISH with RNA-FISH&#160;and immunofluorescence, using peroxidase based signal amplification to accommodate each staining requirement. A major improvement is the ability to obtain, within 10 &#181;m tissue sections, low-background signals that can be imaged at high resolution by confocal microscopy and wide-field conventional epifluorescence. Additionally, the triple staining worked with a wide range of antibodies directed against cellular and viral proteins. The complete protocol takes 2.5 days to accommodate antibody and probe penetration within the tissue.

Detection of the Genome and Transcripts of a Persistent DNA Virus in Neuronal Tissues by Fluorescent In situ Hybridization Combined with Immunostaining

We established a fluorescent in situ hybridization protocol for the detection of a persistent DNA virus genome within tissue sections of animal models. This protocol enables studying infection process by codetection of the viral genome, its RNA products, and viral or cellular proteins within single cells.

Single cell codetection of a gene, its RNA product and cellular regulatory proteins is critical to study gene expression regulation. This is a challenge ...

Pan-lyssavirus Real Time RT-PCR for Rabies Diagnosis

Molecular assays are rapid, sensitive and specific, and have become central to diagnosing rabies. PCR based assays have been utilized for decades to confirm rabies diagnosis but have only recently been accepted by the OIE (World Organisation for Animal Health) as a primary method to detect rabies infection. Real-time RT-PCR assays provide real-time data, and are closed-tube systems, minimizing the risk of contamination during setup. DNA intercalating fluorochrome real-time RT-PCR assays do not require expensive probes, minimizing the cost per sample, and when the primers are designed in conserved regions, assays that are specific across virus genera rather than specific to just one virus species are possible. Here we describe a pan-lyssavirus SYBR real-time RT-PCR assay that detects lyssaviruses across the Lyssavirus genus, including the most divergent viruses IKOV, WCBV and LLEBV. In conjunction with dissociation curve analysis, this assay is sensitive and specific, with the advantage of detecting all lyssavirus species. The assay has been adopted in many diagnostic laboratories with quality assured environments, enabling robust, rapid, sensitive diagnosis of animal and human rabies cases.

This real-time RT-PCR using dsDNA intercalating dye is suitable to diagnose lyssavirus infections. The method begins with RNA extracted from rabies suspected ante-mortem or post-mortem samples, detailing master mix preparation, RNA addition, setup of the real-time machine and correct interpretation of results.

Molecular assays are rapid, sensitive and specific, and have become central to diagnosing rabies. PCR based assays have been utilized for decades to ...

Field Postmortem Rabies Rapid Immunochromatographic Diagnostic Test for Resource-Limited Settings with Further Molecular Applications

Functional rabies surveillance systems are crucial to provide reliable data and increase the political commitment necessary for disease control. To date, animals suspected as rabies-positive must be submitted to a postmortem confirmation using classical or molecular laboratory methods. However, most endemic areas are in low- and middle-income countries where animal rabies diagnosis is restricted to central veterinary laboratories. Poor availability of surveillance infrastructure leads to serious disease underreporting from remote areas. Several diagnostic protocols requiring low technical expertise have been recently developed, providing opportunity to establish rabies diagnosis in decentralized laboratories. We present here a complete protocol for field postmortem diagnosis of animal rabies using a rapid immunochromatographic diagnostic test (RIDT), from brain biopsy sampling to the final interpretation. We complete the protocol by describing a further use of the device for molecular analysis and viral genotyping. RIDT easily detects rabies virus and other lyssaviruses in brain samples. The principle of such tests is simple: brain material is applied on a test strip where gold conjugated antibodies bind specifically to rabies antigens. The antigen-antibody complexes bind further to fixed antibodies on the test line, resulting in a clearly visible purple line. The virus is inactivated in the test strip, but viral RNA can be subsequently extracted. This allows the test strip, rather than the infectious brain sample, to be safely and easily sent to an equipped laboratory for confirmation and molecular typing. Based on a modification of the manufacturer&#39;s protocol, we found increased test sensitivity, reaching 98% compared to the gold standard reference method, the direct immunofluorescence antibody test. The advantages of the test are numerous: rapid, easy-to-use, low cost and no requirement for laboratory infrastructure, such as microscopy or cold-chain compliance. RIDTs represent a useful alternative for areas where reference diagnostic methods are not available.

We present a complete protocol for postmortem diagnosis of animal rabies under field conditions using a rapid immunochromatographic diagnostic test (RIDT), from brain biopsy sampling to final interpretation. We also describe further applications using the device for molecular analysis and viral genotyping.

Functional rabies surveillance systems are crucial to provide reliable data and increase the political commitment necessary for disease control. To date, ...

A Rapid Method for Multispectral Fluorescence Imaging of Frozen Tissue Sections

Multispectral fluorescence imaging on formalin-fixed paraffin-embedded (FFPE) tissues enables the detection of multiple markers in a single tissue sample that can provide information about antigen coexpression and spatial distribution of the markers. However, a lack of suitable antibodies for formalin-fixed tissues may restrict the nature of markers that can be detected. In addition, the staining method is time-consuming. Here we describe a rapid method to perform multispectral fluorescence imaging on frozen tissues. The method includes the fluorophore combinations used, detailed steps for the staining of mouse and human frozen tissues, and the scanning, acquisition, and analysis procedures. For staining analysis, a commercially available semiautomated multispectral fluorescence imaging system is used. Through this method, up to six different markers were stained and detected in a single frozen tissue section. The machine learning analysis software can phenotype cells that can be used for quantitative analysis. The method described here for frozen tissues is useful for the detection of markers that cannot be detected in FFPE tissues or for which antibodies are not available for FFPE tissues.

We describe a rapid staining method to perform multispectral imaging on frozen tissues.

Multispectral fluorescence imaging on formalin-fixed paraffin-embedded (FFPE) tissues enables the detection of multiple markers in a single tissue sample ...

Quick and Early Detection of Rabies Antibodies to Evaluate the Immune Response in a Patient

Detection of Rabies IgG and IgM Antibodies Using the Rabies Indirect Fluorescent Antibody Test

The rabies indirect fluorescent antibody (IFA) test was developed to detect various rabies-specific antibody isotypes in sera or cerebral spinal fluid. This test provides rapid results and can be used to detect rabies antibodies in several different scenarios. The rabies IFA test is especially useful for the quick and early detection of antibodies to evaluate the immune response in a patient who has developed rabies. Although other methods for antemortem rabies diagnosis take precedence, this test may be utilized to demonstrate recent rabies virus exposure through antibody detection. The IFA test does not provide a virus-neutralizing antibody (VNA) titer, but the pre-exposure prophylaxis (PrEP) response can be evaluated through positive or negative antibody presence. This test can be utilized in various situations and can provide results for a number of different targets. In this study, we used several paired serum samples from individuals who received PrEP and demonstrated their rabies antibody presence over time using the IFA test.

Author Spotlight: Rabies-Specific Antibody Isotypes Detection in Sera or Cerebral Spinal Fluid Using an IFA Test 

The aim of this manuscript is to examine the use of the rabies indirect fluorescent antibody test for the detection of rabies-specific IgG and IgM antibodies.

The rabies indirect fluorescent antibody (IFA) test was developed to detect various rabies-specific antibody isotypes in sera or cerebral spinal fluid. ...

Postmortem Diagnosis of Rabies in Animals by the Updated, Multiplexed LN34 Real-Time Reverse Transcription-Polymerase Chain Reaction Assay

Rabies is a fatal zoonotic disease caused by Lyssavirus rabies (RABV) and related negative strand RNA viruses from the Lyssavirus genus (family Rhabdoviridae). The LN34 assay targets the highly conserved leader region and nucleoprotein gene of the lyssavirus genome and utilizes degenerate primers and a TaqMan probe containing locked nucleotides to detect RNA across the diverse Lyssavirus genus. A negative finding for rabies should be made only if a full cross-section of the brain stem and three lobes of the cerebellum are examined; however, identification of lyssavirus RNA in any tissue is diagnostic of rabies infection. Tissue is collected and homogenized in TRIzol reagent, which also inactivates the virus. RNA extraction is performed using a spin column-based commercial extraction kit. Master mixes are prepared in a clean space and aliquoted into a 96 well plate before adding sample RNA. In clinical settings, each sample is tested by real-time RT-PCR for the presence of lyssavirus RNA in triplicate and singly for host &#946; -actin mRNA. Positive and negative controls are included at extraction and real-time RT-PCR steps of the protocol. Data analysis involves manual adjustment of the thresholds to standardize Ct values across instrument runs. Positive results are determined by the presence of typical amplification in the pan-lyssavirus assay (Ct &#8804; 35). Negative results are determined by the absence of typical amplification in the pan-lyssavirus assay and detection of host &#946;-actin mRNA (Ct &#8804; 33). Observation of values outside of these ranges or failure of the assay controls can invalidate the run or result in inconclusive results for a specimen. The protocol should be closely followed to ensure high assay sensitivity and specificity. Procedural modifications can affect assay performance and lead to false positive, false negative, or uninterpretable results.

This protocol demonstrates the pan-lyssavirus LN34 real-time reverse transcription-polymerase chain reaction (RT-PCR) assay from tissue collection to result interpretation, including updates to primer sequences and formulations to improve assay performance for some non-rabies lyssaviruses and lagomorphs. We also demonstrate the assay setup for a single-well LN34 multiplexed (LN34M) format.

Immunohistochemistry Test for the Lyssavirus Antigen Detection from Formalin-Fixed Tissues

Summary

Explore More Videos

Chapters in this video

Evaluation of a Universal Nested Reverse Transcription Polymerase Chain Reaction for the Detection of Lyssaviruses

Standard Operating Procedure for Lyssavirus Surveillance of the Bat Population in Taiwan

Immunohistochemical Analysis in the Rat Central Nervous System and Peripheral Lymph Node Tissue Sections

A Technique to Simultaneously Visualize Virus-Specific CD8+ T Cells and Virus-Infected Cells In situ

Detection of the Genome and Transcripts of a Persistent DNA Virus in Neuronal Tissues by Fluorescent In situ Hybridization Combined with Immunostaining

Pan-lyssavirus Real Time RT-PCR for Rabies Diagnosis

Field Postmortem Rabies Rapid Immunochromatographic Diagnostic Test for Resource-Limited Settings with Further Molecular Applications

A Rapid Method for Multispectral Fluorescence Imaging of Frozen Tissue Sections

Detection of Rabies IgG and IgM Antibodies Using the Rabies Indirect Fluorescent Antibody Test

Postmortem Diagnosis of Rabies in Animals by the Updated, Multiplexed LN34 Real-Time Reverse Transcription-Polymerase Chain Reaction Assay